Signal transformers are nowadays used in a multiplicity of power electronic circuits, in particular in driver circuits for driving power semiconductor switches of converters. In this case, the signal transformer of the driver circuit serves for DC isolation of a signal function generator from the power semiconductor switch to be driven. Such a signal transformer is specified in GB 2 293 933 A, for example, wherein a first signal transformer is provided for DC-isolated transmission of a switch-on signal of the power semiconductor switch and a second signal transformer is provided for DC-isolated transmission of a switch-off signal of the power semiconductor switch. The two signal transformers are customarily embodied with two limbs in each case, the first limb being at least partly enclosed by a primary winding and the second limb being at least partially enclosed by a secondary winding. The two limbs of each such signal transformer are usually connected to one another in such a way that a magnetic circuit is produced, in which a main magnetic flux generated by the respective primary winding can flow.
What is problematic in the case of a signal transformer described above in accordance with GB 2 293 933 A is that this enables only a single primary winding signal present at the primary winding, for example a switch-on signal or a switch-off signal, to be transmitted as a secondary winding signal. However, if the intention is, for example, to provide two secondary winding signals, namely a switch-on signal and a switch-off signal, for example, as in the case of an abovementioned driver circuit for driving a power semiconductor switch, then a signal transformer with a respective signal function generator connected to the primary winding of the signal transformer has to be provided for each secondary winding signal. It is thus not possible to transmit a single primary winding signal on the transformer input side as a plurality of secondary winding signals on the transformer output side. By virtue of the fact that, therefore, only precisely one primary winding signal can be transmitted as a secondary winding signal in the case of a signal transformer described above in accordance with GB 2 293 933 A, when there are a plurality of secondary winding signals to be made available, as in the case of the driver circuit in accordance with GB 2 293 933 A, there is a huge increase in the material costs on account of the number of signal transformers required. A large number of signal transformers is additionally accompanied by an undesirably large space requirement. Furthermore, the availability of an abovementioned driver circuit decreases as the number of signal transformers rises, since the probability of faults increases with an increased number of signal transformers. Finally, this can result in long maintenance times associated with high maintenance costs which are unacceptable for an operator of, for example, a converter with driver circuits of this type.